Closed-loop mosquito insecticide delivery system and method

ABSTRACT

A mobile, real-time, closed-loop system and method for delivering an aerosol insecticide spray to a treatment area during a treatment period of time employs a prime mover having a spray nozzle through which an air volume is produced in order to entrain insecticide as particles in an airstream passing out of the nozzle. A particle size detector, weather centers and an electronic controller are used to regulate the amount of insecticide and particle size dependent upon speed of the prime mover and weather conditions at the treatment area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.09/952,389, filed Sep. 12, 2001 now U.S. Pat. No. 6,669,105 which claimsthe benefit of U.S. Provisional Application No. 60/232,214, filed Sep.13, 2000, both of which are hereby incorporated herein in theirentireties by reference.

BACKGROUND OF THE INVENTION

This invention relates to insect control through the application ofinsecticide and, particularly, to an improved system and method forapplying insecticide from a vehicle to more accurately, safely andcost-effectively eradicate mosquitoes in both rural and cityenvironments.

DESCRIPTION OF THE PRIOR ART

Prior to 1990, open-loop, electronic-based fluid flow rate control wasavailable to the mosquito control industry. The earliest device of thistype was the “PRO-FLO,” a proportional flow rate pump controllerinvented by H. Starr (deceased). Currently available mosquitoinsecticide delivery systems utilize aerosol (i.e., fog) generatorsmounted on a prime mover, such as a truck or other vehicle, to enablespraying to specifically selected sites in rural and city environments.The majority of these systems typically employ a small gas motor, ablower unit for generation of an air flow, a supply tank for theinsecticide and a nozzle assembly which mixes the insecticide chemicalwith the blower-directed air in order to disperse the insecticide asmicron size insecticide fog particles. Recently, a different class ofaerosol generators have become available which use electrical power togenerate the insecticide fog. While the spray results for electricalpower generators are similar to the gas powered spray systems, they aresignificantly quieter during spraying.

Often, the ground vehicle spraying systems are used together withinsecticide spraying via aircraft as part of a comprehensive program toeradicate mosquitoes.

Since mosquito bites can lead to very serious infections (malaria,dengue fever and encephalitis), the requirement for ground vehiclemosquito eradication programs will continue indefinitely. Further, theincrease in the average temperature in both the winter and summer months(due to CO₂ and other greenhouse gases) will steadily increase both theareas and time periods each year when mosquito eradication programs willbe required. A recent example of this increased need for a mosquitoeradication program occurred during 1999 in New York City. Mosquitobites resulted in several cases of encephalitis and consequentially anew comprehensive and continuing mosquito eradication program has beenimplemented for that city.

One major problem associated with presently available ground vehiclemosquito spray systems is that the weather conditions locally at thevehicle are not automatically considered in the spray process. Atpresent, the vehicle operator must decide whether to stop or continuethe spray process if obvious weather problems such as heavy rain exist.However, the vehicle driver in an enclosed air-conditioned vehicle cabmay not be aware of other adverse weather conditions such as wind speedand direction. For example, if the wind on a city street is blowing at90 degrees to the direction of vehicle travel, then one side of thestreet will receive more insecticide concentration and the opposite sideof the street will receive less than planned. Further, particularweather conditions at a spray vehicle may mean that the spraying mustfully stop or that the vehicle must travel in a different direction thanplanned to achieve a desirable spray application in a particular area.

Unfortunately, the information on weather related discrepancies in spraycoverage are not presently available to management. Therefore, nocorrective action can be taken for the level of insecticideconcentration varying widely over a spray process. In addition, thehumidity level and the ground temperature at the vehicle also impact thefog distribution process. These two variables along with wind andvehicle velocity should also be considered continuously to optimize thespraying process. The control interaction with these complex variablesduring a spray operation requires an electronic recorder and controllersystem with the capability to both process intelligent spray controlalgorithms and record and utilize real-time weather information.Effective spray systems with these capabilities have not previously beenavailable.

Such intelligent spray control algorithms are also dependent uponaccurate knowledge of the vehicle geographical position. For example,the decision to spray at a certain concentration (or not spray at all)may depend upon geographical information such as (a) the location ofinsecticide sensitive individuals or animals in the planned spray area,and/or (b) the location of areas which have a high potential formosquitoes such as a stagnant pond. Fortunately, the required accurategeographical knowledge is now universally available to all vehicles inreal-time and at low cost to the electronic recorder and controllersystem via inputs from the U.S. Global Positioning Satellite System(GPS).

Another major problem with presently available aerosol generators is thedifficulty of both generating and verifying the desired droplet size ofthe insecticide. A desired particle size must be maintained whileproviding varying fluid flow rates, which are required in order tomaintain the same concentration of insecticide as the vehicle varies itsspeed while spraying. The droplet size for a particular chemical and themaximum application rate per unit area are determined from regulationsby the U.S. Environmental Protection Agency and/or state and localgovernments. The regulations for droplet size are based upon conflictingrequirements of the effect of the insecticide upon the generalenvironment and the need for a maximum effective kill rate for theinsecticide. The optimum particle size will vary for a particularchemical, for a particular location and for weather conditions, as wellas the type of target mosquito.

The presently available spray technology assumes that the desiredparticle size can be generated by varying the air pressure applied tothe nozzle against a measured fluid flow rate. This technique requires aseries of calibrations of particle size versus air pressure and fluidflow rate for each insecticide type. This control of air pressureapplied to the nozzle for mosquito eradication is implemented in themosquito control industry by two prior art methods, the most common ofwhich is a one-point calibration of a fixed air pressure setting versusa fixed flow rate for a particular chemical. This technique is anopen-loop control process that produces a desired particle size only ata fixed fluid flow rate and at the related vehicle speed. As the vehiclespeed varies during a spray application, the particle sizes may varywidely from the particle size specified in government regulations. Thesecond method requires the addition of an air pressure sensor, apressure regulator valve and a controller to maintain a desired airpressure relative to the vehicle speed and the fluid flow rate. Whilerequiring more equipment and extensive calibrations, this method isstill an open loop approach as the particle size can vary during a sprayprocess and not be detected. An example of this method is disclosed inU.S. Pat. No. 5,248,448 to Waldron et al.

For electrically powered spray systems of the type described above, theparticle size is generated by the rotation rate of a porous cylinderblock located on the rotating shaft. Changes in the particle size isaccomplished by varying the rotation rate of the shaft. This techniqueis still an open loop control system for particle size.

In order to correct these serious problems in vehicle mosquito spraysystems, there is a need for a new system and method which:

(1) Continuously maintains the optimum mosquito insecticide droplet sizeand application rate;

(2) Continuously includes the weather conditions at the vehicle as partof the spray control process;

(3) Continuously includes the geographical position of the vehicle aspart of the spray control process;

(4) Accepts programmable spray process instructions and providesdetailed spray process reports including the concentration ofinsecticides applied at any time and/or at a geographical position; and

(5) Is flexible in design so as to be adaptable for controllinginsecticide particle size and recording data based upon other criteria.

The present invention is directed to a system and method which providesthese and other features.

SUMMARY OF THE INVENTION

A primary objective of this invention is to provide an improved groundvehicle mosquito insecticide spray system and method which ensures thatthe desired spray flow rate at the optimum particle size is effectivelyapplied to the selected area.

Another object of this invention is to provide an insecticide deliverysystem and method which utilizes a closed loop control approach basedupon direct, real-time measurement of the insecticide particle sizebeing delivered by the sprayer.

It is another object of the present invention to provide a system andmethod which supplies detailed reports on the estimated sprayapplication concentrations for all geographical locations that have beenexposed to insecticide spraying.

It is another object of the invention to provide real-time insecticideparticle size measurement data to a Sprayer Recorder and Controller(SRC) unit so that real-time control of the particle size can beachieved.

It is another object of the invention to use a system and method whichprovides local weather information (wind velocity, humidity andtemperature for example) automatically to the vehicle SRC so that thisinformation can be used in real-time in the spray control process. Thisinformation is also be reported as part of the process of accessing theviability of a particular insecticide at a specific location.

It is another object of the invention for the SRC to accept geographicalposition information and related instructions so that real-time controlof the spray process in selected geographical positions is automaticallyachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a typical vehicle with the spray system of thepresent invention mounted on the vehicle with weather sensors, GPSantenna and other components of the system also shown.

FIG. 2 is a block diagram of the spray system of the present invention,including a novel Spray Recorder and Control (SRC) unit in which closedloop control of the spray process is achieved while considering vehiclespeed, fluid flow rate, insecticide particle size, weather andgeographical position.

FIG. 3 is a drawing of the SRC front panel of FIG. 2, showing theoperator keyboard and display interfaces.

FIG. 4 is a logic flow diagram illustrating various logic inputs andoutputs for the Spray Recorder and Control (SRC).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be understood by those skilled in the art that the presentinvention is not limited in its application to the details of theparticular arrangement shown here since the invention is capable ofother modifications and embodiments. The terminology used herein is forthe purpose of description and not of limitation.

FIG. 1 is a view of a typical vehicle 1 with a spray system 2 mounted onthe vehicle. The spray system 2 is mounted on skid 2A for easyinstallation and removal. Weather sensors are mounted on the vehicle aretemperature sensor 3, wind velocity sensor 4, and humidity sensor 5.Also shown on the top of the vehicle 1 is Global Position System (GPS)antenna 6 (a component of the spray system 2).

Weather sensors 3, 4, 5 and GPS antenna 6 are powered by spray system 2.All signal and power cabling from spray system 2 to antenna 6 andweather sensors 3, 4, 5 are weatherproof and are independent of thewiring of vehicle 1, thereby allowing easy installation and removal onany type of prime mover used for spraying.

Also shown on FIG. 1 are other components of the spray system 2. Theseare spray nozzle 7, SRC 8, motor 9, blower 10, air volume control 15,shaft 16 and piping 17.

FIG. 2 is a block diagram of a preferred form of spray system 2,including SRC 8.

Referring to FIG. 2, particle size measurement is achieved by directlymeasuring the size of insecticide particles 11 in real-time at theoutput of nozzle 7. To achieve this measurement, particle analyzer 12 isprovided, having detector 13 directly exposed to the flow of insecticideparticles 11. Particle analyzer 12 provides the measured particle sizeto SRC 8 (upon command) over RS232 cable 14.

Real-time closed loop control of the size of particles 11 is thenachieved by SRC 8 by comparing the particle size as measured by analyzer12 against a desired particle size by SRC 8, in part, from predeterminedcriteria provided by reference to applicable regulations and/ormanufacturer's specifications, and then, if necessary, changing thelevel of an electrical signal to air volume control 15 via control input15A. In response to the change in the electrical level on input 15A toair volume control 15, prime mover 9 increases or decreases the rotationrate of shaft 16. This change in turn modifies the volume of airgenerated by blower 10 and applied via piping 17 to nozzle 7. Thisincrease or decrease of air volume to nozzle 7 directly changes the sizeof insecticide particles 11 and the insecticide fluid being supplied tothe nozzle 7 from insecticide tank 18 via fluid pump 19 and fluid ratesensor 20.

Nozzle 7 may, for example, be in accordance with the design shown inU.S. Pat. No. 5,232,164 to Resch. Nozzles of this type generate adesired particle size by controlling the volume of air applied tonozzle. A second order control not required over the range of mosquitoinsecticide particles is to maintain the depth of liquid film on thenozzle surfaces. The optimum particle size may also be controlledwithout the measurement and control of the air pressure at the spraynozzle.

For electrically powered spray systems of the type discussed above, thereal-time closed loop control of the particle size is achieved byvarying the rotation rate of the shaft on which the porous cylinder ismounted. The loop is then closed by the measurement of the particlesize, which is then supplied to SRC 8.

Real-time particle size measurement is utilized as the primary variablein the control loop to ensure that the spray system 2 does not emit aninsecticide particle size 11 that may be a danger to the environment andto reduce insecticide waste from a particle size 11 that does notprovide the maximum mosquito kill. The use of a primary variable forclosed loop control normally provides a more cost efficient and reliablesystem and method. Refer to U.S. Pat. Nos. 5,667,558 and 5,667,651 toBryan for a recent example of the benefit of using the primary systemoutput for closed loop control. In the systems disclosed in thesepatents, the cost of chemicals in wastewater scrubber applications hasbeen reduced by approximately 50%. This is accomplished by measuring andcontrolling the level of H₂S gas (the system output) rather than theindirect variable, the level of pH in the scrubber sump. These patents,both of which are incorporated here by reference, are now in extensiveuse in the U.S. wastewater industry.

Referring again to FIG. 2, the desired insecticide fluid flow rate to beapplied to nozzle 7 is achieved by a second closed loop subsystem. TheSRC 8 calculates the desired flow rate from the vehicle speed, vehiclegeographical position determined from GPS antenna 6, and the desiredinsecticide concentration at these position and weather conditionsdetermined from temperature sensor 3, wind velocity sensor 4 andhumidity sensor 5. The SRC 8 then turns on pump 19 via cable 21 to forceinsecticide in tank 18 to nozzle 7. The insecticide fluid flow rate isdetected by pump rate sensor 20 and passed to the SRC 8 via cable 22.SRC 8 controls this flow rate loop independently of the size ofparticles 11. This is achieved because the conversion of fluid 18 toparticles 11 is almost independent of air volume changes required forparticle size control.

Referring again to FIG. 2, SRC 8 continuously receives data from weathersensors 3, 4 and 5. The weather sensor information is continuouslyrelated by the SRC 8 to previously programmed management decisions onthe weather limits for the spray process. Specifically, the decision forstopping or continuing the spray process is not totally dependent upon ajudgment of weather factors by the operator of vehicle 1.

Information from temperature sensor 3 enables the spray system 2 torespond to a particular insecticide suggested requirement (normallyprovided by the chemical manufacturer) for only spraying within certaintemperature limits. Humidity sensor 4 enables a spray operation that mayproceed even in light rain, and wind velocity sensor 5 is used toidentify wind velocity limits for spraying established by themanufacturer.

Novel algorithms are required in SRC 8 to process the weather data fromsensors 3, 4, and 5, and utilize the data in a spray process. Forexample, it is necessary to separate the velocity of vehicle 1 from thewind velocity while the spraying is in process. Vehicle position andspeed information provided by GPS receiver 24 is combined with the datafrom wind velocity sensor 4 to determine the wind velocity effect on thespraying process in real-time.

A set of novel algorithms are required in the SRC 8 to process andintegrate the vehicle local weather data from sensors 3, 4, 5, thevehicle geographical position from GPS receiver 24, the real-timemeasurement and control of insecticide particle size from analyzer 12and concentration and the specific spray trip control data frominstructions 27.

The digital memory SRC 8 has in (pre-trip preparation) been loaded withtrip instructions 27 for the geographical areas to be sprayed. For eacharea, the trip instructions 27 provide the geographical spray start andstop positions, the speed limits while spraying, required insecticideparticle size, required insecticide concentration, wind velocity anddirection limits, temperature and humidity limits for spraying and thetype of insecticide to be sprayed. Note that the trip instructions 27will significantly vary for each area dependent upon the composition ofthe area (i.e., swamp or city street) and other local sprayrestrictions.

Per FIG. 2, the GPS receiver 24 upon SRC 8 command (every 2 seconds)provides position data and vehicle speed 28 to the SRC. The SRC 8 thencompares the GPS position information for each spray area's geographicalstart and stop position and uses this unique information to obtain fromSRC memory, the trip instructions that apply to the vehicle's currentposition.

Refer to FIG. 4 for a diagram of the novel algorithm to control thespray process at an area designated as Area X.

FIG. 4 shows the GPS processed position data 28 is compared every 2seconds with the Area X specified position. If in agreement, for thestart position for Area X, the SRC 8 immediately initializes theparameters 30 for the Area X and enters the spray process loop controlalgorithm 31. The spray process algorithm uses the initialization data30 to set the insecticide particle size 37, insecticide flow rate(concentration) 38, the vehicle speed limits 36, and prior to sprayingaccepts and verifies that the vehicle local weather conditions 32 arewithin trip specifications.

While in the spray process loop algorithm 31, the SRC 8 accepts datafrom the GPS equipment 28, weather instrument 32, the flow rate sensor33, particle size measurement 34 and processes this data to determine ifany spray control changes are required. If spray control changes arerequired, the SRC spray process loop 31 can (as discussed in FIG. 2)vary the particle size 36, the flow rate 35 or turn on an alarm tocontrol spray process speed.

Further, if the weather conditions change such that trip instructionsare violated or if insecticide particle size or flow rate are notcontrollable (possibly due to equipment failure), the spray processalgorithm stops the spray process and informs the operator of theproblem.

Also shown on FIG. 2, RS-232 duplex communications link 25 to the SRC 8enables management to input spray process decisions for particle size,insecticide concentration limits, geographical information for aparticular spray area and weather control. This information is combinedwith the spray control algorithms in SRC 8 to control the spray processand to inform the driver of vehicle 1 in real-time of the spray processvariables.

RS-232 duplex communications 25 also provides a detailed report on theresults of a particular spray process (referred to as a spray tripreport). It is expected management will provide a computer processingsystem to accept a detailed report on all variables in the spray processsuch as insecticide usage, estimated insecticide concentration atselected geographical positions, weather conditions during the sprayprocess, start and stop time periods of spraying, and so forth. Thisinformation is then available to automatically generate instructions forthe next spray trip in a particular area. Spray trip reports wereavailable to the mosquito control industry prior to 1990 in thepreviously noted PRO-FLO system, invented by H. Starr.

Refer to FIG. 3 for display and keyboard 28 used with SRC 8. Theinformation on the display 28 provides fluid flow rate, vehicle speed,position, and weather data, and indicates if the spray is off or onsince the spray may be turned off (e.g.; at a particular location). Itshould be noticed that if the spray is off, the vehicle is moving, andthe spray process enabled then an audible alarm would also be sounded toalert the driver.

This concludes the description of the preferred embodiments. A readingby those skilled in the art will bring to mind various changes withoutdeparting from the spirit and scope of the invention. It is intended,however, that the invention only be limited by the following appendedclaims.

1. A closed-loop system for delivering an insect spray to a treatmentarea, the system comprising: means for producing an aerosol spray of theinsecticide at the treatment area during a treatment period of time;means for controlling the aerosol spray producing means responsive toreal-time weather conditions at the treatment area during the treatmentperiod; and means for controlling the aerosol spray producing meansresponsive to the real-time size of insecticide particles in the aerosolspray during the treatment period.
 2. The system recited in claim 1,wherein the means for controlling the aerosol producing means responsiveto the real-time size of insecticide particles in the aerosol spraycomprises: a particle detector positioned to measure the size ofinsecticide particles in the spray; and means for receiving an outputfrom the particle detector and providing an input representativethereof.
 3. The system recited in claim 2, wherein the means forcontrolling the aerosol spray producing means comprises means forcomparing a desired particle size to the detected particle size.
 4. Thesystem recited in claim 1, wherein the weather conditions comprise oneor more of wind speed, wind direction, temperature and humidity.
 5. Thesystem recited in claim 4, further comprising: a prime mover for movingthe spray system through the treatment area during the treatment period;means mounted on the prime mover for sensing the weather conditions andproviding an electronic output representative thereof; and an electroniccontroller for receiving the electronic output control signals to themeans for controlling the aerosol producing spray means.
 6. The systemrecited in claim 1, further comprising: a prime mover for moving thespray system through the treatment area during the treatment period;means for controlling the aerosol spray producing means responsive tothe real-time speed of the prime mover while moving through thetreatment area during the treatment period.
 7. A closed-loop method fordelivering an insect spray to a treatment area, the method comprisingthe steps of: producing an aerosol spray of the insecticide at thetreatment area during a treatment period of time; controlling the outputof the aerosol spray responsive to real-time weather conditions at thetreatment area during the treatment period; and controlling the aerosolspray output responsive to the real-time size of insecticide particlesin the aerosol spray during the treatment period.
 8. A closed-loopsystem for delivering an insect spray to a treatment area, the systemcomprising: an aerosol spray producer of insecticide responsive toreal-time weather conditions at a treatment area during a treatmentperiod; and a controller for controlling the aerosol spray producerresponsive to a real-time size of insecticide particles in the aerosolspray during the treatment period.
 9. The system recited in claim 8,wherein the controller comprises a particle detector positioned tomeasure the size of insecticide particles in the spray.
 10. The systemrecited in claim 9, wherein the controller comprises means for comparinga desired particle size to the detected particle size.
 11. The systemrecited in claim 8, wherein the weather conditions comprise one or moreof wind speed, wind direction, temperature and humidity.
 12. The systemrecited in claim 11, further comprising a prime mover for moving thespray system through the treatment area during the treatment period. 13.The system recited in claim 8, further comprising a prime mover formoving the spray system through the treatment area during the treatmentperiod.